Gaseous electric discharge lamp



IA.RUT'IIENAUER 2, 3 2

GAS'EOUS ELECTRIC DISCHARGE'LAMP Filed Aug. ",7, 1955 "INVENTOR OQuMQuQ/O RNEY' Patented Feb. 11, 1936 casaousnmzcrmc nrscnanda Lam Alfred Biittenauer, Berlin-Halensee, Germany, assignor to General Electric company, a oorpo ratlonof New York Application August I. 1935, Serial No; 35,181: I Germany August 20, 1934 1' comma. '(01. 176 -122) a g i of vwhich is light emitting during the operation present invention relates. to gaseous electric discharge lamps generally and. more particularly the invention relates to such devices having luminescent material associated there-- 5 with which material is excited to luminescence 15 ting qualities unchanged during the useful life of the gaseous electric discharge lamp. Still further objects and advantages attaching to the device and'to its, use and operation will be apparent to those skilled in the art from the fol 20' lowing particular description.

I have discovered that a gaseous electric. discharge lainp having a fluorescent coating consisting of' a mixture of from 90 to 97% of the yellowish-white form. of zinc silicate and from to 3% of a blue fluorescent material, such as calcium tungstate, emits a white light and that this coating does not disintegrate nor change its light emitting characteristics during the operating life of the gaseous electric discharge 30 lamp. The quantity of the blue fluorescent material,- such as calcium tungstate, added to the zinc silicate depends upon the thickness of the coating of the fluorescent material on the lamp container. It is desirable to have the fluorescent 35 coating of such depth that substantially all of the ultra-violet rays emitted by the gaseous-electric discharge are absorbed thereby and transformed into visible light and substantially all the visible light rays emitted by said discharge are -40 transmitted thereby. Usually about 7% of calcium tungstate is effective. Lamps made in accordance withthe present invention are useful for illuminating purposes and theattractive white appearance thereof is 45 useful in advertising, as in signs v In the drawing accompanying and forming part of this specification an embodiment of the invention is shown in a side elevational, partly sectional view.

50 Referring to the drawing the lamp comprises an elongated, tubular container i having electrodes I and l sealed into the ends thereof and .nja aseous atmosphere therein comprising a such as mon'r quantity M 65 voporlsable material, such asf mercury, the vapor of the device. Said electrodes 2 and 3 are sinter'ed mixtures of electron emitting material,

'suclras barium oxide, and high melting-point material, such as tungsten, are electron emitting 5 whenatan elevated temperature and are heated to the operating, electron emitting temperature thereof bythe voltage drop thereat and current flow therethrough. When desired, cold, sheet metal electrodes are used.

. l0 Said container I has a fluorescent coating 4 on the inner surface thereof which coatingv consists of the mixture of fluorescent materials disclosed above. The coating 4 is applied to the inner surface of said container l by methods now known in the art, such as by heating the container l to the softening temperature and propelling particles of the fluorescent material toward thesoftened inner surface of said container i so that the particles are partially-embedded in said surface, as disclosed in co-pending application, Serial Number 758,514, fl1ed December 20, 1934 or by partially embedding the fluorescent materialin a layer of light transmitting enamel applied to the inner surface of said container i and having 5 a lower softening temperature than said container I, as disclosed in co-pending application Serial Number 758,028, filed December 18, 1934;. As pointed out above the fluorescent coating should be of sumcient thickness to transform substantially all of the effective ultra-violet rays mitted by the gaseous electric discharge in the lamp to visible light rays and yet should be thin enough to transmit all the visible light emitted by said discharge. A lamp having the above structure appears white and emits a substantially white light during the operation thereof.

It will be understood, of course, that numerous changes in the form and details of the device and in its use and operation maybe made by those 40 skilled in the art without departure from the spirit and scope of the invention, for example, the coating 4 is applied to the outer surface of said container I, when desired, or the fluorescent material is applied to a light transmitting screen mounted separate from but in ultra-violet light receiving relation to thelamp, when desired. In these modifications of the invention the container I must .be made of an ultra-violet transmitting material such as quartz. I

What I claim as new and desireto secure by Letters Patent of the United States, is:-- g 1 l. A gaseous cl *trlc'discharge lamp comprisin: a container, electrodes sealed therein, a gaseous atmosphere therein" capable of emitting.vi sa ible rays andultra-violet rays when excited by an electric discharge between said electrodes; a coating otfluorescent material associated therewith, said coating consisting of a mixture of from 90 to 977% of the yellowish-white form of zinc silicate and from 10 to 3% of calcium tungstate.

2. A gaseous electric discharge'lamp comprisin: a container, electrodes sealed therein, a gaseous atmosphere therein capable of emitting vis ible rays and ultra-violet rays when excited by an electric discharge between saidelectrodes, a coating of fluorescent material associated there with, said coating consisting of a mixture 01 from 90' to 97% of the yellowish-white form of zinc silicate and 7% calcium tungstate.

ALFRED RUI'I'ENA UER. 

